1. Field of the Invention
The present invention relates to a constant velocity universal joint for use in any application requiring torque transmission through a varying angle. More particularly, the invention involves a universal joint that utilizes a plurality of balls to transmit a torque from an inner joint member to an outer joint member. The interior of the outer joint member contains a series of grooves that are in radial alignment with a complementary series of grooves that are positioned on the exterior of the inner joint member. A cage is positioned between the outer joint member and the inner joint member to guide the balls as they traverse the grooves during articulation of the universal joint.
2. Description of the Prior Art
The prior art reveals a wide variety of devices that permit the transmission of a rotational torque from one shaft that is angularly displaced with respect to another shaft coupled thereto. In general, most of the prior art devices require extensive machining of the individual parts to assure satisfactory assembly and operation of the device. Then, too, the overall strength of the prior art devices was compromised by the required machining of the individual parts.
The present invention differs from the undercut-free constant velocity joint that is shown and described in U.S. Pat. No. 3,879,960, entitled "Constant Velocity Joint" issued Apr. 29, 1975, to Hans-Heinrich Welschof et al. The constant velocity joint described in the above-referenced patent shows an outer joint member in which the individual ball grooves are divergent with respect to the central axis of the universal joint, when viewed from the open end of the outer joint member. The ball grooves that are positioned in the inner joint member are convergent with respect to the central axis of the universal joint. The balls are maintained in a spaced apart planar relationship with one another by means of a cage that is positioned between the outer joint member and the inner joint member. The outer joint member does not lend itself to press forging techniques since the opening therein is of smaller diameter than the diameter of the interior cavity therein. Also, the lip of the outer joint member is thin because of the divergent nature of the ball grooves. The thin areas of the outer joint member occur at one of the areas of maximum stress in the universal joint, particularly when large angles of articulation are employed.
Thus, the present invention differs from the above-described universal joint in that the divergence and convergence of the ball grooves in the outer joint member and the inner joint member are in reverse order. Then, too, the free end of the outer joint member is of increased thickness in the present invention.
In U.S. Pat. No. 4,188,803, entitled "Constant Velocity Universal Joint" issued Feb. 19, 1980, to Nobuyuki Otsuka et al, there is shown a universal joint that employs an input and an output shaft. The output shaft has a cavity containing hub into which is fitted the end of the input shaft. The input shaft contains an inner member attached thereto. The inside of the hub and the outside of the inner member contain ball grooves. A ball cage is positioned between the hub and the inner member. The ball cage is unique in that its inside and outside surfaces contain spherical surfaces that are eccentric instead of the usual concentric spherical surfaces. The ball cage is supported on spherical surfaces that are also eccentric.
The present invention utilizes substantially concentric spherical surfaces. Further, the present invention does not have any undercuts that must be made in the hub area as does the above reference. The ball cage of the present invention is quite simple with concentric spherical surfaces being employed. Also, the hub and inner torque members utilize concentric spherical surfaces.
Another example of the prior art is shown in U.S. Pat. No. 4,610,643, entitled "Rotary Constant Velocity Universal Joint" issued Sep. 9, 1986, to Werner Krude. The universal joint shown in the U.S. Pat. No. 4,610,643 has an outer joint member in which the ball grooves are convergent as viewed from the open end of the outer joint member and the grooves in the inner joint member are divergent. This arrangement or slope of the grooves is just the opposite to that seen in the previously discussed U.S. Pat. No. 3,879,960. The outer joint member is separate from the axle-hub combination with which it coacts. A cylindrical sleeve unites the outer joint member to the hub by welding and crimping techniques. A ball cage supporting element is used to retain the balls in the grooves to engage the balls on one side. The ball cage supporting element does not contact the spherical surfaces of the outer joint member or the inner joint member, but instead, the ball cage contacts a spherical surface 30 in the interior of the joint near the central hub as shown in FIG. 1. In the above-described patent, the ball cage contains a series of fingers that are intercalated with respect to the balls. This universal joint requires extensive machingin to fabricate the joint as well as complicated tools for fabricating the various details.
The present invention is an improvement over the universal joint shown and described in the U.S. Pat. No. 4,610,643, in that fewer parts are utilized and there is less frictional contact with the ball cage. Additionally, the present invention provides a ball cage with apertures therein that completely circumscribes each ball. Further, by providing a universal joint with an outer joint member having a thick structural section near its open end, the area of highest load concentration upon articulation, the joint is more reliable and durable. The outer joint member fabrication is simplified and the cost of fabrication is significantly reduced.